Tamper-resistant Software Watermarking Technique Based On Code Encryption Research And Realization

Software watermarking is the kind of technique to protect the copyright of software. Traditional software watermarking has some limitations on tamperproofing, the data rate, robustness and stealth. This thesis focuses on the above issues of applying watermarking to software protection. In order to enhance the ability of copyright protection, tamperproofing software watermarking scheme which is based on code encryption has been proposed.This thesis compares dynamic software watermarking with static software watermarking, and studies of watermark data split algorithm, the topology structure of dynamic graph watermarking, as well as the process of embedding and extracting watermark. A new method of improving the data rate of PPCT structure has been proposed. For enhancing the tamproofing ability, software watermarking and code encryption are combined together. The accomplished researches are as follows:First of all, study of the graph topology structure of dynamic graph watermarking, and propose an improved topology structure, named MPPCT. Compared to the PPCT, MPPCT shows the advantage of data rate and resistance to collusive attack.Secondly, in order to improve the tamperproofing and enhance the difficulty of reverse engineering analysis, a novel approach of tamper-resistant software watermarking is proposed, which is based on the code encryption technique. The watermarking is embedded into a program by modifying its source code and binary code. According to our strategy, part of the code is chosen to encrypt, and the encryption key is tightly related to the program.In addition, we design and implement a prototype system which is called MPPCTMark, and then we conduct a lot of test cases. According to the experiment results, we analyse the validity, robustness, data rate and performance overload which caused by the embedded watermark, the result verifies the feasibility and validity of the scheme that proposed.